The present invention relates to a device subject to pushing a thermocompression bonding tool against a lead of an electronic part to be connected to a printed circuit board.
Examples of a technique for mounting a driving circuit through thermocompression bonding include a technique for mounting an IC module of a liquid crystal display. The liquid crystal display is generally obtained by connecting a driving circuit to a TFT liquid crystal module interposing liquid crystal material between two glass substrates and superposing them on an illuminating device. In general, the driving circuit of the TFT (thin film transistor) liquid crystal module is constituted by a tape-shaped film carrier package (TCP) provided with an LSI for driving TFTs and a printed circuit board (PCB) for sending power and image signals to the TFT module. FIG. 3 is a diagram showing the structure of a driving circuit section of a conventional TFT liquid crystal module. The reference numeral 1 denotes a TFT substrate on which a plurality of source electrodes and gate electrodes are formed, the reference numeral 2 denotes a color filter, the reference numerals 3 and 4 denote ACF (anisotropic conductive films) in which conductive particles are distributed into adhesive material, the reference numeral 5 denotes a driving LSI, the reference numeral 6 denotes TCPs provided with the driving LSI and having input terminals and output terminals, and the reference numeral 7 denotes the printed circuit boards. The ACF 3 is bonded to a terminal section of the TFT substrate 1 where the TCPs 6 are aligned and temporarily compression bonded one by one. Then, a plurality of TCPs 6 arranged in a line along one end face of the TFT substrate 1 are permanently compression-bonded and heated collectively by using one heater tool and are thereby connected to the TFT substrate 1. By the process in which TCPs 6 arranged in a line along the end face of the TFT substrate 1 are permanently compression bonded collectively, the number of manufacturing steps can be reduced.
When a TFT terminal electrode is connected to the TCP by using the above-mentioned method, a temperature gradient is generated between a panel end of a TCP lead and a central part thereof. Therefore, the lead is deformed to have an L shape at the panel end and is thus connected. For this reason, although a terminal of a glass substrate is parallel with the TCP lead before the connection, a mutual non-parallel portion is generated due to the deformation after the thermocompression bonding so that an electrode of the substrates and the TCP lead which should be originally adjacent but be apart come in contact with each other and are electrically short-circuited. In some cases, consequently, a liquid crystal module is not operated normally. The following countermeasures have been taken for such a shift of the TCP lead.
In the invention described in Japanese Unexamined Patent Publication No. 265023/1993, width and pitch of the TCP leads are changed so as to gradually increase toward both ends of a terminal arrangement. Thus, the influence of a terminal shift caused by the thermal expansion of a TCP is reduced.
In the invention described in Japanese Unexamined Patent Publication No. 206878/1998, an electrode of a glass substrate is formed to have a width reduced gradually toward an end of a lead line. Thus, also in the case in which a TCP is mounted with an oblique shift, an electrode comes in contact with an adjacent lead is avoided.
In the invention described in Japanese Unexamined Patent Publication No. 260421/1998, electrodes of a glass substrate are arranged like a fan. Thus, a terminal shift between the electrode of the glass substrate and a TCP lead can be reduced.
In the invention described in the Japanese Unexamined Patent Publication No. 265023/1993, however, a countermeasure is taken for only the shift in a parallel direction of the terminal of the glass substrate and the TCP lead, and is not effective for a terminal shift in an oblique direction. In the invention described in the Japanese Unexamined Patent Publication No. 206878/1998, if the mounting is carried out obliquely, there is a problem in that an overlap area of the electrode with the lead is reduced and the connecting reliability of the terminal is deteriorated. In the invention described in the Japanese Unexamined Patent Publication No. 260421/1998, the electrodes of the glass substrate are arranged like a rectilinear fan. This shape is not identical to that of the TCP lead which is obtained after the thermocompression bonding. Actually, the TCP lead has a shape shown in FIG. 1(b) after the thermocompression bonding. Since the TCP leads have a uniform high temperature during the compression bonding from a tip portion thereof to a central part thereof (see 8a of FIG. 1B), they are arranged in almost parallel with each other. Since the temperature during the compression bonding is gradually dropped from the vicinity apart from a glass substrate end by 0.3 mm toward the glass substrate end (see 8b of FIG. 1B), the whole TCP leads are bent to have an “L” shape toward the inside in this portion. In particular, the above-mentioned shape is more remarkable in a closer portion to both ends of the terminal arrangement. In the invention described in the Japanese Unexamined Patent Publication No. 260421/1998, the electrodes are formed like a rectilinear fan. However, the shape of the TCP lead is different from that of the glass substrate electrode after the compression bonding. Therefore, this invention is insufficient for the countermeasure to be taken for the terminal shift.
It is an object of the present invention to provide liquid crystal display and method of manufacturing the same in which a positional shift of a glass substrate electrode and a TCP lead can be prevented from being generated due to deformation during compression bonding.